Resilience to temperature and pH changes in a future climate change scenario in six strains of the polar diatom Fragilariopsis cylindrus

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Marina Pančić, Per Juel Hansen, Anna Tammilehto, Nina Lundholm

Abstract. The effects of ocean acidification and increased
temperature on physiology of six strains of the polar diatom
Fragilariopsis cylindrus from Greenland were investigated.
Experiments were performed under manipulated pH levels
(8.0, 7.7, 7.4, and 7.1) and different temperatures (1, 5, and
8 C) to simulate changes from present to plausible future
levels. Each of the 12 scenarios was run for 7 days, and a significant
interaction between temperature and pH on growth
was detected. By combining increased temperature and acidification,
the two factors counterbalanced each other, and
therefore no effect on the growth rates was found. However,
the growth rates increased with elevated temperatures
by 20–50% depending on the strain. In addition, a general
negative effect of increasing acidification on growth was observed.
At pH 7.7 and 7.4, the growth response varied considerably
among strains. However, a more uniform response was
detected at pH 7.1 with most of the strains exhibiting reduced
growth rates by 20–37% compared to pH 8.0. It should be
emphasized that a significant interaction between temperature
and pH was found, meaning that the combination of the
two parameters affected growth differently than when considering
one at a time. Based on these results, we anticipate
that the polar diatom F. cylindrus will be unaffected by
changes in temperature and pH within the range expected by
the end of the century. In each simulated scenario, the variation
in growth rates among the strains was larger than the
variation observed due to the whole range of changes in either
pH or temperature. Climate change may therefore not
affect the species as such, but may lead to changes in the
population structure of the species, with the strains exhibiting
high phenotypic plasticity, in terms of temperature and
pH tolerance towards future conditions, dominating the population.
Original languageEnglish
Article number12
JournalBiogeosciences
Volume12
Pages (from-to)4235-4244
Number of pages10
ISSN1726-4170
DOIs
Publication statusPublished - 2015

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